(13–14) “But if they turn away, say, ‘I warn you of a thunderbolt like the thunderbolt that struck Ād and Thamūd.’ * The messengers came to them from before them and from behind them, proclaiming, ‘Worship none but Allah.’ They said, ‘Had our Lord willed, He would have sent down angels. We therefore disbelieve in that with which you have been sent.’”

That is, if these deniers turn away after the praiseworthy qualities of the Quran and the attributes of the Magnificent God have been made clear to them, “say, ‘I warn you of a thunderbolt’”—that is, a punishment that will eradicate and overwhelm you—“like the thunderbolt that struck Ād and Thamūd,” the two well-known peoples. Punishment swept them away, and grievous retribution befell them because of their wrongdoing and disbelief.

“The messengers came to them from before them and from behind them”—that is, one following another in succession, all bearing the same call: “Worship none but Allah.” In other words, they commanded them to devote worship sincerely to Allah and forbade them to associate partners with Him. Yet they rejected their message and denied them, saying, “Had our Lord willed, He would have sent down angels”—meaning: as for you, you are merely human beings like us—“We therefore disbelieve in that with which you have been sent.” This specious argument has continued to be inherited by deniers [among the nations] (1). It is among the flimsiest of arguments, for being an angel is not a prerequisite for being sent as a messenger. The only requirement of messengership is that the messenger bring evidence demonstrating his truthfulness. Let them, then, if they can, impugn the messengers’ truthfulness on rational or scriptural grounds—but they will never find a way to do so.